It's important to keep the rubber side down.

I don't think I would take turns at 30 mph on my hybrid, but on a road bike with good tires, not too worn, it can be done relatively safely (anything happening at 30mph on a bike can only be relatively safe) if you follow Eden's advice. The pedal on the inside of the turn should be up and the other pedal (obviously) should be down with all your weight on it. Keeping your body upright is also important. I do that while in the drops, with my weight far towards the back of my bike, with my fingers ready to feather the brakes. However braking while in the curve would be a very bad idea and create a high risk of skidding...

It takes some practice and also some foolishness at first, but it can absolutely be done with proper technique and, I want to emphasize it again, good road tires, preferably in dry conditions. I wouldn't trust a wet pavement for that sort of downhilling..